Rx solution

In response to the letter of June 2, your correspondent is puzzled about the following correction prescribed for an optometrically normal 12-year-old: RE +0.50DS 1 base down LE +0.50DS 1 base down. It is probable that the prescription derives from the Skeffington/optometric extension programme concept that near vision is intrinsically stressful.1 It is argued that this stress results in a tendency for over convergence and that prescribing 'low plus', typically R&L +0.50DS, supplements the accommodation up to the desired plane of convergence. This restores the balance between accommodation and convergence and relieves the stress. The yoked prism, bases in the same direction, is probably intended to influence head and body posture. Base-down yoked prism is thought to create 'expanded peripheral awareness, relaxation, outwards and backwards body thrust and increased near point working distance'. In a review of the literature for the College of Optometrists I have been unable to find any evidence beyond the anecdotal in support of either 'low-plus' or 'yoked-prism' prescriptions. J A M Jennings UMIST, Manchester Reference 1 Birnbaum MH. (1993) Optometric management of nearpoint vision disorders. Butterworth-Heinemann, Stoneham, MA 02180, US. - Note: A full review of this topic will be published in the August 2000 edition of Optometry in Practice, the College of Optometrist's CET Journal.